3. Focus Performance and Accuracy
As a professional wildlife photographer, autofocus is one of the most important things that I look for in a lens/camera combination. These days even the most basic lenses are capable of solid focusing performance, primarily when used in good light. However, the top-of-the-line lenses really come into their own (along with the better camera bodies) when they can focus accurately under challenging conditions. Conditions such as low light, fast-moving subjects, and complex backgrounds require lenses that make the most of the camera’s tracking capabilities, and I am rarely satisfied with the performance of prosumer telephoto lenses in this regard.
Coming into this review, I was skeptical about the ability of the Sigma 100-400mm F/5-6.3 DG OS HSM C’s to keep up in demanding situations. This was mainly due to the somewhat dim max aperture of f/6.3 at the telephoto end of the focal range along with my prior experience with Sigma’s HSM autofocus motor which I have always found to be behind the best autofocus motors from Canon, Nikon, and Sony when it comes to getting the most reliable focus tracking performance. After getting the chance to test the Sigma 100-400mm F/5-6.3 DG OS HSM C in the field, I can report that the overall performance is quite decent for most applications, but the autofocus is unsurprisingly sluggish when shooting in low light.
When shooting in One-Shot AF (AF-S), the lens focuses relatively quickly in all but low light shooting situations and with reasonable accuracy. I had no problems nailing the White-Tailed Deer in the first frame of this article even though some branches obstruct his face. However, things change when light levels drop, and in such situations, the focus behavior is somewhat sluggish with noticeable hunting. This performance is not unexpected for a slow telephoto zoom lens. Also, I did notice quite a lot of hunting when trying to focus on a subject that is near the minimum focus distance, and in such situations, the Canon EF 100-400 f/4.5-5.6L USM IS II offers an appreciably more reassuring performance.
Shooting in AI-Servo (AF-C continuous) focus, the lens turns in a mixed result, with solid focus acquisition speed but comparatively inconsistent accuracy. This is especially noticeable when shooting challenging subjects that move erratically. In such situations, there is a marked dip in the ratio of shots in perfect focus (even when using high performing camera bodies like the Canon 1Dx).
When photographing Canadian Geese in flight, the Sigma lens had no problems quickly latching onto them, and for the most part, it did an admirable job keeping them in proper focus. Canadian geese are large birds and are relatively easy to track, and in good light with a dominant subject in the frame against an uncomplicated background, the ratio of shots in good focus is more than satisfactory. However, you’ll find yourself frustrated when trying to track a problematic subject in less than ideal conditions. In such cases, a lens like Canon’s 100-400mm f/4.5-5.6L USM IS II beats the Sigma handily.
4. Image Quality
The versatility of the 100-400mm focal length makes it highly adaptable for a range of photographic applications, but designing a lens with such a focal range that offers high image quality at all of its focal lengths is a genuine challenge. Based on its highly attractive price and Sigma’s excellent track record in recent years, I was keen to find out just how well the Sigma 100-400mm F/5-6.3 DG OS HSM C performed when it came to its sharpness characteristics. I was especially intrigued to see how well it would hold up at the all-important 400mm focal length. In short, the Sigma lens is a good performer with a relatively even performance across all focal lengths.
At 100mm at f/5, the sharpness characteristic is very good in and around the center of the frame. You gain a little bit of extra sharpness around the center and mid-frame when stopping down to f/8, where results are nearly excellent. The story is different in the periphery of the frame where the lens is fairly soft. Unfortunately, the corners of the frame only gain a very small amount of extra sharpness when stopping down and you actually increase the level of lateral chromatic abberation when doing so. Diffraction starts affecting image sharpness by f/11.
100mm f/5:
At 200mm and f/5.6, sharpness remains at very good levels in the center of the frame. Once again, you get a little bit of extra sharpness in the center when stopping down to f/8, where results are nearly excellent. The quality in the periphery of the frame substantially improves from the performance at 100mm with good levels of sharpness right out from f/5.6. By f/8, the corners nearly reach “very good” levels of sharpness, and you get nice, even performance across the entirety of the frame.
200mm f/5.6:
At 300mm and f/6.3, the sharpness characteristic is on a good level in the center of the frame. You gain a small increase in sharpness when stopping down to f/8, where the lens shows very good levels of sharpness. The quality in the periphery of the frame takes a step back from that of the 200mm setting, with a hint of softness at f/6.3 and decent sharpness by f/8.
300mm f/6.3:
An essential part of any 100-400mm lens is the performance at 400mm, and here the Sigma turns in a surprisingly good performance. Central sharpness is decent at f/6.3. By f/8, the sharpness in the center of the frame improves quite a bit, and we get good to very good levels of sharpness. When looking closely at the F/8 center crops, you can clearly see the patterns and textures of the paper used to make the map. At f/11, there is a slight decrease in central sharpness. The corners of the frame are fairly soft at f/6.3, but they become sharper and sharper at f/8 and f/11.
400mm f/6.3:
Overall, the Sigma 100-400mm F/5-6.3 DG OS HSM Contemporary turns in a convincing performance when it comes to its sharpness characteristics. This is especially true when you consider the performance relative to its price tag; in many ways, the Sigma lens competes on a similar level with lenses that are more than twice as expensive. The quality in the center of the frame is consistently good to very good at all focal lengths, and while the corners are quite weak at 100mm, they catch up nicely at 200mm and 300mm.
*The last set of crops was done indoors, as the lack of a dedicated tripod collar makes it harder to take test shots outside.
5. Vibration Reduction
The Sigma 100-400mm F/5-6.3 DG OS HSM C comes with Sigma’s Optical Stabilization (OS) system. Usually, a lens manufacturer specifies the number of stops of stabilization which their lens is rated for, but Sigma hasn’t given any exact numbers with this lens. Shooting at 100mm, I was able to get a decent keeper rate at around 1/15 of a second and at 400mm I was able to get to around 1/50s. This performance seems to indicate about 3-4 stops of image stabilization, which is a little on the low side these days.There are two stabilization mode settings to be found on the lens. Mode 1 is your default stabilization, while Mode 2 is for panning.
A unique feature of Sigma lenses is their compatibility with the Sigma USB dock which permits you to change some of the lens’s behavior, including the Optical Stabilization. With the lens plugged in, you are allowed to choose between three different OS settings which are described by Sigma as follows:
- Dynamic View Mode: This mode offers a recognizable OS effect to the image in the viewfinder. This helps to ensure the composition of images quickly.
- Standard: This is the default setting. The OS effect is well-balanced and suitable for various scenes.
- Moderate View Mode: This mode offers an excellent compensation of camera shake, and achieves very smooth transition of the image in the viewfinder. The composition of the image remains natural even when the angle of view keeps changing.
While Standard Mode is the default setting, it does have one significant flaw: There is little to no stabilization in the viewfinder. One of the main advantages of having optical stabilization in a telephoto lens is having a stabilized viewfinder as this makes getting an accurate composition at long focal lengths a lot easier. Therefore, my personal choice of the OS setting is the Dynamic View Mode which offers better stabilization in the viewfinder and makes handholding the lens a lot easier.
6. Bokeh
Zoom lenses of this type are not usually known for the quality of their bokeh, but the Sigma 100-400mm f/5-6.3 HSM DG OS Contemporary delivers a nice performance. Variable aperture telephoto-zoom lenses tend to suffer from busy highlight discs with a pronounced “onion ring” effect, but the rounded 9-blade aperture of the lens creates nicely-rounded specular highlights, and the inner zones are reasonably smooth. The lens also delivers a relatively smooth blur in areas of focus transition, with this especially noteworthy in the bokeh of foreground areas.
7. Vignetting
The lens exhibits a moderate amount of vignetting of around 1 to 1.5 stops at the extreme ends of the range with the lens wide-open. Stopping the lens to f/8 resolves most of the corner darkening.
8. Flaring
Due to its complex optical design, the Sigma 100-400mm f/5-6.3 HSM DG OS C struggles a bit when it comes to its handling of lens flare. The performance is about in line with what you can expect from a lens of this type, and you should be aware of the flaring artifacts when the lens is pointed at a bright source of light.
The below crop of the center of the frame of a shot taken of the setting sun clearly shows signs of flare.
9. Chromatic Aberration
Modern lenses have become increasingly good at mitigating chromatic aberration, and the Sigma lens offers reasonable performance in this regard. Lateral chromatic aberration is well controlled in the frame center, where it is virtually nonexistent. The corners of the frame show a higher degree of chromatic aberration (especially at the 100mm and 400mm settings where it’s modestly noticeable), but even at its worst, the performance is undoubtedly reasonable and quite easily corrected in Photoshop.
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